1. Field
This application is directed generally to wireless communications systems. More particularly, but not exclusively, the present application is directed to methods and apparatus for interference mitigation in femtocells operating adjacent to other wireless networks.
2. Relevant Background
Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, video and the like. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, third generation partnership project (3GPP) Long Term Evolution (LTE) systems, as well as other orthogonal frequency division multiple access (OFDMA) systems.
A wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals, which are also known as mobiles, user equipment or UEs. Each terminal communicates with one or more base stations via transmissions on forward and reverse links. The forward link (also known as a downlink) refers to the communication link from the base stations to the terminals, and the reverse link (also know as an uplink) refers to the communication link from the terminals to the base stations. These communication links may be established via systems including single-in-single-out, single-in-multiple-out, multiple-in-single-out or multiple-in-multiple-out (MIMO) systems.
In addition to the mobile phone networks currently in place, a new class of small base stations has emerged. These may be installed in a more local environment, such as a user's home or office environment to provide indoor wireless coverage to UEs in conjunction with existing broadband Internet connections. These miniature base stations are generally known as access point base stations or alternatively as Home Node Bs (HNBs), Home evolved Node Bs (HeNBs), or femtocells. Typically, these miniature base stations are connected to the Internet and the mobile operator's network via broadband connections such as DSL, router or cable modem.
These miniature base stations may be deployed by users in homes, offices or other buildings or local areas, and may be subject to interference from other femtocells, picocells, macrocells and/or other wireless networks. They may also create interference in these other networks. Accordingly, there is a need in the art for methods and apparatus for interference mitigation between these wireless networks.